Overview of Evolution
Many people consider evolution as a theory. They say that evolution has never been proven. I think they are wrong, and in this post, I’m presenting hard evidence that concepts or principles of evolution have been proven.
The principles of evolution say that changes to an organism can, over a long period of time, change the organism such that it becomes a new organism. In order to produce a new organism, the changes or mutations have to be passed on to subsequent generations of the organism. This passing on of the changes is influenced by “natural selection”, and natural selection causes the mutations that favor continued existence of the organism to be preserved over mutations that do not favor continued existence of the organism.
Think of evolution this way. Many, if not most, life forms begin as a single cell. That cell divides and divides and divides, and so on. As the cells divide, the DNA of the organism controls how the cells develop such that some cells become muscles while other cells become bone, and so on. The DNA controls the formation of the organism such that it becomes the same type of organism as the one that originally formed the single cell. However, if mutations occur in the DNA, the resulting organism may be slightly different than the original organism. Over time, these differences can accumulate such that the organism actually becomes a different organism. For example, bone may grow where there was no bone before. The new organism may develop lungs instead of gills and thus be able to exist on dry land. The result of this is that the original organism has evolved into a new organism.
Evolution via Avida
Generally, evolution requires tens of thousands or more generations of the organism before new organisms are created. Because a new human generation only appears after about 20 years, it isn’t practical for scientists to observe evolution in humans. However, some scientists have turned to computer software as a way to study evolution. I’m not talking about computer simulations of evolution. I’m talking about actual evolution in which the computer-generated organisms are changed and new generations are created. Trust me on this, because I worked in industry and education as a computer programmer (software engineer) for over 40 years, and I understand how computer software works. Because computers are fast, new generations can be produced in a fraction of a second, and evolution over tens of thousands of generations can be observed in a relatively short time.
Scientists are using small computer programs, known as “digital organisms,” that behave in certain aspects like real organisms. The digital organisms can reproduce or replicate themselves, and they pass to their descendants changes in their nature that result from mutations caused by external stimuli. The digital organisms are not simulations of evolution in which reactions to stimuli are programmed into the organisms a priori. The organisms actually experience mutations and natural selection, and they react to those stimuli in ways that are not programmed into them.
The software used by the scientists is called Avida. In discussing Avida, we must realize that the software was designed to explore concepts involved in evolution rather than perform evolution of real-life. Numerous articles have been written about digital organisms. I am drawing on an article in Discover magazine for most of my information about Avida. A single digital organism is created with only one skill, the ability to reproduce or replicate itself. The organism reproduces itself, and its children reproduce themselves. Over time thousands of generations of organisms are produced. During these replications, random changes or mutations to the computer commands that make up the organisms occur, and these mutations change the nature of the computer programs and hence the nature of the organisms. These mutations are passed from generation to generation. As mutations change the computer programs of the organisms, new skills are gained by the organisms.
To understand the changes, we have to understand how the computer commands that make up the organisms are organized. We can, in a simplified way, think of there being two groups of computer commands, namely, commands that allow the organisms to replicate themselves, and no-operation commands that consume computer processing power but don’t do anything useful. Mutations occur in both groups of commands. Mutations that occur in the commands causing reproduction may eventually change the commands such that reproduction can no longer occur, and the organisms in those strains die. Mutations in the no-operation commands create new commands, and it is these new commands that lead to the evolution of desirable skills. To understand how the mutations occur, let us realize that the computer programs that make up the organisms are just groups of binary numbers (1 and 0) that are interpreted in particular ways by the computer hardware. The mutations change a 1 to a 0 and a 0 to a 1.
The organisms are fed input numbers. In the beginning, the organisms don’t know how to obtain the numbers or how to do anything with the numbers. As new skills are evolved, the organisms are able to access the numbers and do desirable manipulations of the numbers, such as obtaining a second number, adding the two numbers, etc.
As organisms develop desirable changes in their computer commands, they experience a form of natural selection by being rewarded with increases in the computer processing power that is used by the programs, and this enables those organisms to reproduce at a faster rate. This increases the number of children that have the desirable traits. In the real world, organisms experience natural selection when they evolve traits that enable them to have a higher rate of survival.
Because the digital organisms are experiencing evolution, there are two interesting parallels between them and real-life organisms. The article in Discover magazine discusses these parallels.
Real-life organisms have DNA that contains instructions for passing the genetic nature of the organisms to their descendants. Digital organisms are computer programs that contain commands for passing the computer programs to their descendants; this program defines the nature of the digital organisms.
Mutations to DNA occur which change the genetic nature of the descendants. Mutations to the computer programs occur which change the nature of the digital organisms.
A Research Platform
Scientists are using the Avida software to study evolution. An experiment was conducted to see if digital organisms could evolve into more complex organisms. This experiment was described in the Discover article. The goal of the experiment was to see if digital organisms could evolve into organisms that could determine if two consecutive input numbers are the same. For example, the group of numbers 6190443279 has one pair of equal numbers (44). To provide the conditions for natural selection, Avida was adjusted to reward simple mutations that could lead to the desired complex organism and to give even larger rewards for more complex mutations. The organisms were allowed to replicate for 16,000 generations. This experiment was repeated 50 times, and a complex organism evolved in 23 out of the 50 times. The initial digital organism had only the ability to replicate itself. The complex organism had the additional abilities to obtain the input numbers, keep the last number in its memory, obtain a new number, compare the two numbers, and record in some way if a match occurred or not. An interesting aspect of the experiment is that the 23 successful digital organisms were different from each other because they took different evolutionary paths to reach the desired complexity.
The researcher conducting this experiment calculated that the probability of a complex organism being obtained with random mutations but no natural selection was about one in a thousand trillion trillion. This probability was computed from the number of bits (1 and 0) in a computer program written by the researcher to perform the complex function. This extremely low probability for a complex organism illustrates that the success of 23 out of 50 runs of the experiment was due to natural selection via the rewards given for favorable mutations and the higher rewards for complex mutations. The importance of natural selection was confirmed when the researcher took away the rewards for the simpler mutations–the complex organism was never achieved.